#1 I have the same machine, and its very heavy. Rethink your bench because its not a bench top machine. Someone on here and he has just posted it, built one from steel and welded. I ordered the factory stand and its some assy required but its beefy and also has combo levering feet casters.
#2 NEMA 34 mounts? Are those the rack and pinion gear drive?
#3 All your order is from China, I am hoping it all works for you. You can source good motors from USA Venders and have a warranty. But they look very nice, the ones you ordered.
#4 Your switching dual power supply from your computer is more than likely not going to work. Those NEMA 34 motors and you need 4 of them powered at one time on some jobs will need some serious amps. I have 2 power supplies that are 48 volt and rated at 600 watts each or 12.5 amps each. I have the same machine but ordered prewired control panel and it all works fine from 120 volts. Save your 220 for your dust collector!!
Plug and Play NEMA 34 CNC Control System - CRP800-00E-8 | CNCRouterParts